Dairy products, calcium and the risk of breast cancer: results of the French SU.VI.MAX prospective study

The aim was to estimate the association between dairy products (total and their subgroups), calcium intake and the risk of breast cancer. As few studies have considered menopausal status, we also investigated stratified analyses. This analysis included 3,627 women from the French SU.VI.MAX study, among whom 92 developed breast cancer during the follow-up period. Food consumption was assessed based on five 24-hour records completed during the previous 18 months to follow-up. Calcium intake was calculated using an ad-hoc food composition database. Cox proportional hazards models were used to estimate relative risk (RR), comparing 4th quartile vs. 1st quartile, and 95% confidence intervals (95% CI). A lower risk of breast cancer was observed with high total dairy product consumption in the whole population (RR = 0.55, 95% CI = 0.29-1.03, p(trend) = 0.03) and among premenopausal women with a RR of 0.35 (95% CI = 0.12-0.95, p(trend) = 0.01). None of these associations remained after control for calcium intake. Increasing calcium intake was inversely associated with breast cancer risk considering the whole population (RR = 0.50, 95% CI = 0.27-0.91, p(trend) = 0.04) and among the subgroup of premenopausal women (RR = 0.26, 95% CI = 0.10-0.71, p(trend) = 0.01) respectively. Our data support the hypothesis that dairy products, through calcium content or a correlated component, might have a negative association with the risk of breast cancer, particularly among premenopausal women.